RICHLAND — Not enough is known to decide on the best and most economical way to treat much of the low-activity radioactive waste in Hanford’s underground tanks, said a committee of the National Academies of Sciences.

Still, a decision may need to be made soon to be ready to treat the waste on schedule, it said.

The Hanford nuclear reservation near Richland has 56 million gallons of radioactive and hazardous chemical waste stored in underground tanks from the past production of plutonium for the nation’s weapons program.

The Department of Energy plans to separate the waste into high level radioactive and low activity radioactive waste for treatment at the $17 billion vitrification plant under construction in the center of the Hanford site.

But the plant was not planned to be large enough to treat all the low activity waste. Options include expanding the plant or finding supplemental treatments for the waste to provide additional treatment capacity by 2034.

The National Academies of Sciences committee has prepared a final draft analysis of a study ordered by Congress that looked at three ways to treat the waste and found that vitrifying, or glassifying, the waste for disposal would be considerably more expensive than other options.

The study of treatment options prepared under the leadership of the Savannah River National Laboratory in South Carolina is a good starting point for making a decision on how to treat millions of gallons of Hanford low-activity radioactive waste, the National Academies of Sciences committee said in its analysis.

Treatment costs uncertain

But the report, which is only in draft form so far, does not yet provide the complete technical basis needed to support a final decision on a treatment approach, nor does it clearly lay out a framework of decisions to be made among treatment technologies, waste forms and disposal locations, the committee concluded.

Among the report’s findings was that vitrification, grouting waste into a concrete-like form or using “fluidized bed steam reforming” to turn it into ceramic-like particles are each potential options.

But grouting and steam reforming would be significantly less expensive, it found.

The committee cautioned that cost estimates are based on technologies that, for the most part, have not yet been fully developed or deployed and are based on costs from similar technologies and consistent funding.

“There are large attendant uncertainties, suggesting that costs could be much higher than estimated, but are unlikely to be much lower,” the committee analysis said.

It also noted that a decision on a technology may need to be made soon to make sure that design, construction and startup for any treatment facility is completed by a target date of 2034.

The tank waste is expected to be about 90 percent low activity radioactive waste, which contains less than 10 percent of the tank waste radioactivity.

The vitrification plant, or Waste Treatment Plant, might not have the capacity to treat as much as half of the low activity radioactive waste in a reasonable time.

If the vitrification plant were expanded, the cost would be $20 billion to $36 billion, according to the report reviewed by the commission.

Steam reforming is the least technically mature of the three processes, and grouting would create large amounts of treated waste for disposal.

Disposal options include a lined landfill at Hanford, but the Washington state Department of Ecology has been adamant that any waste form disposed of there must be “as good as glass” from vitrification to protect the groundwater beneath it for hundreds or thousands of years.

Out-of-state disposal also is potentially possible, including at the Clive radioactive waste disposal facility in Utah, if the treated waste meets requirements to be consider Class A low level radioactive waste, the least hazardous classification.

The Waste Control Specialists disposal facility in Texas also could be an option and already has accepted three gallons of Hanford low activity radioactive waste grouted in the initial phase of a pilot project.

The National Academies of Sciences committee recommended that the completed report it reviewed form the basis for further work to pick the best treatment option.

The committee will be in Richland for a meeting Oct. 31 to hear from organizations and others interested in Hanford site cleanup. The Savannah River-led team that prepared the study of treatment options will present its final report.

Public comments on the National Academies of Sciences committee’s review can be submitted until Oct. 31 at bit.ly/LAWcomment or mailed to ATTN: Dr. Charles Ferguson, Nuclear and Radiation Studies Board, The National Academies, 500 5th St. NW, Washington, D.C. 20001.

Comments also may be submitted at the 8:30 a.m. to 5 p.m. Oct. 31 meeting at the Courtyard Richland Columbia Point.